- 218 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



much information has been gained about various insect enemies of 

 the pecan ; and extensive experiments have been made in orchards on 

 the control of these species. 



Cranberry insects. — Investigations of cranberry insects in New 

 Jersey have been continued, and material progress made. The field 

 t-tation was changed from Pemberton to Brown Mills, N. J., during 

 the latter part of 1915. The so-called blackhead fireworm was unus- 

 ually abundant and destructive, but it seems that spraying infested 

 bogs with 40 per cent nicotine sulphate while the insects are in the 

 larval stage is effective. The cranberry rootworm, the cranberry tip- 

 worm, and the bloom worm have also been studied. 



Orchard insecticides and spraying machinery. — This work has 

 been continued and has included the testing of miscellaneous proprie- 

 tary insecticides and further testing of combinations developed in 

 the bureau. In cooperation with the bureaus of Chemistry and Plant 

 Industry, extensive studies are in progress of the arsenical and other 

 poisonous sprajr residues present on fruits at harvest time. Chemical 

 examinations are being made of apples, pears, peaches, grapes, and 

 other fruits of known spray history. The general subject of the com- 

 parative merits of dust versus liquid sprays in orchards and vine- 

 yards has been investigated. In cooperation with the apiculturist of 

 the bureau an investigation has been made of the effect on the honey- 

 bee of spraying apples with arsenicals, during bloom and after fall- 

 ing of most of the petals, according to orchard practice. When the 

 trees are sprayed in full bloom many bees seem to be killed. Spray- 

 ing at the customary time under normal conditions has no injurious 

 effects on the bees. 



Study has been made of the insecticidal constituents of plants, in 

 cooperation with the Bureau of Plant Industry. 



Natural agencies in the control or orchard insects. — Special 

 study has been made of the parasites and predaceous insects which 

 assist in controlling orchard pests. In addition, an investigation has 

 been begun of the fungous diseases of insects, an expert being em- 

 ployed for this purpose. 



Nursery insect investigations. — Special attention has been di- 

 rected to the treatment of the woolly aphis on the roots of nursery 

 apple stock by the use of poisonous gases. The use of carbon bisul- 

 phid has been found to be impracticable under nursery conditions. 

 Tests of para-dichlorobenzene in nurseries against this pest show 

 promise. While heavy dosages kill the young trees, applications of 

 the powder at the rate of from 1 to 5 grams per tree appear to be safe 

 and effective in destroying from 95 to 100 per cent of the insects. The 

 odor of para-dichlorobenzene remains in the soil for at least two 

 months and apparently prevents the reinfestation of the roots during 

 that time. 



SOUTHERN FIELD-CROP INSECT INVESTIGATIONS. 



Investigations of Southern field-crop insects were continued, as 

 in former years, under the direct charge of Dr. W. D. Hunter. 



Cotton insects. — The principal pest considered in relation to 

 cotton culture was the boll weevil. During the year investigation 



